CMake: Fix inconsistent copy ctor/operator=

Detected by GCC9.

Looks like inCMakeCache was left out by mistake in df62701801.

Change-Id: I231d0d3e102edb95b657aef42c3f2f2f834514a0
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cmakeprojectmanager/builddirparameters.h

@@ -44,6 +44,7 @@ public:
     BuildDirParameters();
     BuildDirParameters(CMakeBuildConfiguration *bc);
     BuildDirParameters(const BuildDirParameters &other);
+    BuildDirParameters &operator=(const BuildDirParameters &other);
 
     bool isValid() const;
     CMakeTool *cmakeTool() const;